Human Skeleton

 The Human Skeleton

The human skeleton (see Figures 3.5 and 3.6) can be considered to have two main divisions—the axial and the appendicular skeleton. The axial portion is made of bones in the central or longitudinal axis; the skull, vertebrae, ribs, and sternum. Tiny bones (os-sicles) located in the middle ear and the hyoid bone, located in the neck, are also part of this division. 


The appendicular skeleton is made up of bones that form the appendices—the limbs—and includes the bones that attach the limb to the axial skeleton: the bonesof the shoulder and pelvic girdle and the bones of the upper and lower limb.


The skeletal system consists of 206 bones, of which approximately 40% (80 bones) is part of the axial skeleton. The axial skeleton creates a framework that supports and protects delicate organs of the body and provides a large surface area for the attachment of muscles. Muscles that alter the position of the head, neck, and trunk; those that perform respiratory movements; and muscles that stabilize the position of the limbs when they move are all attached to the axial skeleton. The joints between the bones of the axial skeleton are strong and allow only limited movement.

Comments

Post a Comment

Popular posts from this blog

The Pulmonary Circulation - Anatomy of the Respiratory System

Image
  THE PULMONARY CIRCULATION The blood reaching the alveoli is that of the pulmonary circulation . Blood that has circulated through the body, with most of the oxygen removed, enters the right ventricle via the superior and inferior vena cava. Contraction of the right ventricle pumps this blood into the pulmonary trunk. The pulmonary trunk divides into right and left branches, which take the blood to the right and left lungs, respectively. As in all organs, the arteries divide to form arterioles and capillaries. It is this network of capillaries that sur-round the alveoli and participate in gas exchange. The capillaries join and rejoin to form venules and veins. Ultimately, four pulmonary veins  transport the oxygenated blood into the leftatrium, where they enter the left ventricle and then are pumped into the aorta and distributed to the rest of the body. Bronchial arteries—branches from the aorta—bring oxygenated blood to the bronchi and other lung tissue. Most blood from the bronchia
Read more

Cranial Nerves

Image
  Cranial Nerves Cranial nerves are part of the peripheral nervous system, which is connected to the brain. Twelve pair of cranial nerves arise from the ventrolateral aspect of the brain (Figure 5.37E). The cranial nerves are num-bered according to their position in the longitudinal axis of the brain, beginning at the cerebrum. Each nerve is named, the name being related to the ap-pearance or function. Similar to the spinal nerves, the cranial nerves may carry sensory fibers, motor fibers, or both; some carry fibers with autonomic function. The sensory nerves synapse at the brainstem or join the ascending sensory tracts from the rest of the body to reach the thalamus and cerebral cortex. In addition to sensory nerves that carry sensations such as pain, temperature, touch-pressure, some cranial nerves carry impulses generated by special sense or- gans located in the eye (vision), ear (hearing and bal-ance), nose (smell), and tongue (taste). The motor nerves, such as those in the spinal
Read more